Way to safeguard against hardware (tensile tester) damage in case of Labview failure?

[Purdue17]

Hello,

I am programming a tensile tester program in Labview, but a though occurred to me.  If Labview started to hang or crash, the tensile tester would just move at whatever its last command was; this could destroy the tester motor or load cell.  Is there a safeguard in Labview that would protect me from this?  Or do I have to rig something mechanical to prevent this?

Thanks! 

[Wayne.C]

Purdue17,

Not sure what kind of load cell you are using, but we use mechanical limiters for load cells on our motor dynes.  These limiters control how far a load cell can be deflected.  As far as your program goes, is this going to run on a PC?

[AnalogKid2DigitalMan]

Some commercial tensile testers have limits you can set in the program to terminate the test when a limit is exceeded.

If not, then suggest using a shear pin, torque limiting clutch, or breakaway motor coupler to limit load to the motor. Or use a comparator circuit and latch that moitors the load cell output and when a threshold is exceeded then trip a relay to remove power to the motor.

-AK2DM

[nathand]

If you're running on a PC, LabVIEW isn't your only potential source of failure - you don't know what else is running on the machine that might cause it to crash.  One place I worked put a simple timer connected to the main power relay on every system.  The timer was connected to a digital output that was driven by the software.  A pulse on the digital output caused the timer to reset.  If the timer expired (it didn't see a pulse in the right period of time), its output turned off, killing power to the system.

[tbob]

Protection against hardware damage is something for which you do not want to rely upon software.  AK2DM's answer is the best of all.  Hardware protection will give you the most reliable protection.